Humans responsible for the desertification of the Sahara: Where available, the evidence suggests that there is systematic homogenization of the floral composition of terminal AHP landscapes commensurate with the spread of shrubbery and reduced precipitation. Subsistence choices were predicated on ecological conditions, and early pastoral economies took root against the backdrop of a progressively drying climate. Because humans have been documented as exerting significant pressures on the NPP of prehistoric and historic landscapes elsewhere in
Large-scale teleconnections: Here it is shown that deforestation of tropical regions significantly affects precipitation at mid- and high latitudes through hydrometeorological teleconnections. In particular, it is found that the deforestation of Amazonia and Central Africa severely reduces rainfall in the lower U.S. Midwest during the spring and summer seasons and in the upper U.S. Midwest during the winter and spring, respectively, when water is crucial for agricultural productivity in these regions. Deforestation of Southeast Asia
More forests, more rain: …that implementing measured characteristics of a successful semi-arid afforestation system (2000 ha, ~300 mm mean annual precipitation) over large areas (~200 million ha) of similar precipitation levels in the Sahel and North Australia leads to the weakening and shifting of regional low-level jets, enhancing moisture penetration and precipitation (+0.8 ± 0.1 mm d−1 over the Sahel and +0.4 ± 0.1 mm d−1 over North Australia), influencing areas larger than the original afforestation.
Recognition of aerial rivers: Given the city’s population growth scenarios, the increase of the renewable water resource by smart reforestation could cover 22–59% of the additional demand by 2030. Building on the findings, we argue for a more systematic consideration of aerial river connections between regions in reforestation and land planning for future challenges.
Evapotranspiration: In the Sahel, recycling of moisture through evapotranspiration appears to be responsible for more than 90% of the rainfall. As a result, there exists an important feedback mechanism between land-use and climate, which has immediate implications for the management of natural resources.
Megacities depend on downwind evapotranspiration: Our results reveal that 19 of 29 megacities depend for more than a third of their water supply on evaporation from land. We also show that for many of the megacities, the terrestrial dependence is higher in dry years. This high dependence on terrestrial evaporation for their precipitation exposes these cities to potential land-use change that could reduce the evaporation that generates precipitation. […] reveals four highly vulnerable megacities (Karachi,
Puhh…. Most rain on the Iberian peninsula falls in winter as wet, low-pressure systems blow in from the Atlantic. But a high-pressure system off the coast, called the Azores high, can block the wet weather fronts. The researchers found that winters featuring “extremely large” Azores highs have increased dramatically from one winter in 10 before 1850 to one in four since 1980. These extremes also push the wet weather northwards, making downpours in the northern
Nonlocal effects: Deforestation influences surface temperature at the location of deforestation (local effects) and elsewhere (nonlocal effects). […] Using simulations in a climate model, we show that deforestation-induced changes in the brightness of the surface influence surface temperature mainly nonlocally and thus may be largely overlooked in observation-based data sets. The simulations show that the nonlocal effects have a larger impact on global average surface temperature than the local effects, independent of how much area
Let it (possibly) rain: Some bacteria have the unique capacity of synthesising ice-nucleation-active (INA) proteins and exposing them at their outer membrane surface. […] During 14 precipitation events, strains affiliated with the genus Pseudomonas, which are known to carry INA genes, were dominant. A screening for INA properties revealed that ~12% of the cultivable bacteria caused ice formation at ≤-7 °C. They had likely been emitted to the atmosphere from terrestrial surfaces, e.g. by convective
Scientists found in their study that the global food system was responsible for 16 billion metric tons of greenhouse gas emissions in 2018, or a third of all global emissions that year. This is a sharp contrast to the more narrowly defined agriculture sector of the IPCC’s categories for greenhouse gas inventories, which accounted for 5.3 billion metric tons in 2018, or just a tenth of the total. “The national greenhouse gas inventories, [under] the
Stable forests: We argue that resource and finance allocation for stable forests should be incorporated into countries’ and donors’ comprehensive portfolios aimed at tackling deforestation and forest degradation as well as resulting emissions. Key policy insights: Climate policies, finance, and implementation have tended to focus on areas of recent forest loss and near-term threats of anthropogenic disturbance, resulting in an imbalance of effort that fails to adequately address stable forests. In some contexts, policy measures
Concept of precipitationsheds, defined as the upwind atmosphere and surface that contributes evaporation to a specific location’s precipitation.: We illustrate the importance of upwind land cover in precipitationsheds to sustain precipitation in critically water stressed downwind areas, specifically dryland agricultural areas. […] This work demonstrates that seemingly separate parts of Earth’s biophysical system are interlinked with its social systems. Indeed, our results and analysis suggest that food security in some of the world’s most water-constrained
Mind the difference between air temperature measured in 2m height and at the ground: Ecological research heavily relies on coarse-gridded climate data based on standard- ized temperature measurements recorded at 2 m height in open landscapes. However, many organisms experience environmental conditions that differ substantially from those captured by these macroclimatic (i.e. free air) temperature grids. […]. We found that sub-canopy air tem- peratures differ substantially from free-air temperatures, being on average 2.1°C (standard deviation
Been out again yesterday, and made a few new measurements. Astonishing the high temperatures on the open ground with >50°C – as hot as the asphalt. And also fascinating the comparison between “on the mulch” and “under the mulch” for vegetables: 24°C difference.
Disappearing groundwater requires action to prevent widespread water scarcity Groundwater is the primary water source for billions of people and for nearly half of irrigated agriculture, yet its incon- spicuous presence has allowed groundwater to elude effective governance and manage- ment in countless regions around the world. Consequently, more than half of the world’s major aquifers are being depleted, some of them at an alarming pace.
More forest, more stable rains: We found a significant buffering effect of forests in the precipitation variability of 10 out of 14 biomes globally. On average, if 50% of precipitation originates from forest, then we find a reduction in the coefficient of variation of monthly precipitation of 60%. We also observed that a high fraction of precipitation from non-forest land sources tends to have the opposite effect, that is, no buffering effect. The average variation
Forests and their impacts on low level clouds: However, changing the forest cover can further affect the climate system through biophysical effects. One such effect that is seldom studied is how afforestation can alter the cloud regime, which can potentially have repercussions on the hydrological cycle, the surface radiation budget and on planetary albedo itself. Here we provide a global scale assessment of this effect derived from satellite remote sensing observations. We show that for
My presentation on “Working with plants, soils and water to cool the climate and rehydrate Earth’s landscapes“. As it looks, we have a pretty exciting tool in the climate as well as agriculture discussion with multiple benefits: more vegetation (especially in agriculture; through undersowing, intercropping, agroforestry, but also through a different form of animal husbandry, forest conversion, water retention) means more fertile soils, more water storage capacity and infiltration, more nutrients, more habitat for insects
Interesting analysis: Here, we carefully analyze the situation for reforestation and afforestation (R&A) at midlatitudes, where the warming effects due to vegetation albedo are regarded to be almost balanced by the cooling effects from an increased carbon storage. Using both satellite data and atmospheric boundary-layer models, we show that by including cloudalbedo effects due to land–atmosphere interactions, the R&A cooling at midlatitudes becomes prevalent. This points to a much greater potential of R&A for wet
My UNEP paper on “Working with plants, soils and water to cool the climate and rehydrate Earth’s landscapes“. The continued destruction of forests, the deterioration of soils, the subsequent loss of terrestrial soil water storage and the reduction of water retention in the landscape are disrupting the movement of water in and through the atmosphere. This disruption causes major shifts in precipitation that could lead to less rainfall and more droughts in many areas of the world,
